Venus and Jupiter rendezvous in the west at nightfall

Alan Pickup

Author: Alan Pickup

The maps show the sky at 23.00 GMT on the 1st, 22.00 GMT on the 16th and 21.00 GMT (22.00 BST) on the 31st. An arrow shows the motion of Mars while Venus’ position is shown at the month’s end. Summer time begins at 01.00 GMT on the 26th when clocks go forward one hour to 02.00 BST

The two brightest planets, Venus and Jupiter, are meeting in a memorable conjunction in our western evening sky as March begins, while Mars still stands high in the south at nightfall above the unmistakable form of Orion. However, the Sun is moving northwards at its fastest for the year and the days are lengthening, so that, by the month’s end, Orion stands well over in the south-west as it gets dark.

Comet 2022 E3 (ZTF) was a spectacular photographic object and a marginal naked-eye one a month ago, but is now visible only through telescopes to the south-west of Orion as it recedes, never to return again.

Venus, Moon and Jupiter conjunction

Venus, Moon and Jupiter conjunction 22 Feb 2023, Mark Phillips

Our focus this time is on Venus and Jupiter. Venus, the brighter of the two, was slow to climb into view after rounding the Sun’s far side in October but is now obvious in the western sky at nightfall and destined to remain as a so-called evening star until it dives towards the Sun’s near side in July. At magnitude -4.0, it outshines every other nighttime object bar the Moon and can even by seen in daylight, if we know where to look. Still pulling away from the Sun, its altitude at Edinburgh’s sunset improves from 24° tomorrow to 30° on the 31st.

At magnitude -2.1, Jupiter is around one fifth as bright as Venus and sinking lower in our evening sky as it moves towards the Sun’s far side in April. The other giant planet, Saturn, passed beyond the Sun in mid-February but remains too low in our morning twilight to be seen in March.

Jupiter stands only 0.6°, or just more than a Moon’s breadth, to Venus’s left on the first evening of the month. Both worlds lie in the same telescopic field of view with the dazzling disk of Venus appearing 12 arcseconds across and 86% illuminated at its distance of 205 million km. Jupiter, though, is 864 million km away and 34 arcseconds wide with its four main moons in line from upper-left to lower-right. On the 2nd, look for Jupiter 0.8° below Venus with the four moons still on show.

Conjunctions between these two planets occur in most years, but very few are as close or as well placed in our sky. Indeed, I was surprised to discover that Scotland must wait until November 2039 for a good view of a closer conjunction between the pair, and we’ll need to rise before dawn to see it.


Moon lit by earthshine, Mark Phillips

As the month goes on, Jupiter dips lower into our evening twilight so that by the 22nd it is only 3° high in the west one hour after sunset. The very slender earthlit Moon lies just below it on that evening and stands above and to its left, and below-right of Venus a day later.

Jupiter sets only one hour after the Sun on the 27th when binoculars may reveal Mercury 1.5° to its right and shining at magnitude -1.4. The smallest planet climbs a little higher each evening as it emerges for its best evening apparition of the year in April.

The Sun crosses northwards over the equator at 21:24 GMT on the 20th, the moment of the spring or vernal equinox for Earth’s northern hemisphere. Sunrise/sunset times for Edinburgh this month change from 07:05/17:46 GMT on the 1st to 06:47/19:48 BST (05:47/18:48 GMT) on the 31st, following our switch to British Summer Time on the 26th.

The Moon is full on the 7th, at last quarter on the 15th, new on the 21st and at first quarter on the 29th.

Our star maps show views of the northern and southern halves of the sky in the late evening, when Orion is dipping towards to the western horizon and it is Leo’s turn to have pride of place on the meridian (due south) as the Plough it about to reach the zenith. Follow a curving line downwards along the handle of the Plough, past the famous naked-eye double star formed by Alcor and Mizar, and extend it to the bright orange giant star Arcturus in Bootes and onwards to blue-white Spica in Virgo.

Leo’s leading star, Regulus, is also blue-white and stands in the handle of the Sickle of Leo, the backwards stellar question mark that represents the lion’s head and mane. Here we find the double star Algieba, one of the finest in the sky.

Viewed through binoculars or with the naked eye, Algieba has a fainter neighbour less than a Moon’s breadth to its south. This star, labelled 40 Leonis, lies 69 light years away and is not gravitationally linked to Algieba which lies another 57 light years beyond. In fact, we need a telescope to glimpse the true Algieba double whose two stars lie less than 5 arcseconds apart and orbit each other every 510 years – since it was discovered by Sir William Herschel in 1782, they have almost completed half an orbit. Both component stars are Arcturus-like giants, cooler, larger and much brighter than our Sun.

Mars lies due west at our map times as its motion (shown by the arrow) carries it 14° eastwards from between the horns of Taurus and into Gemini. It dims from magnitude 0.4 to 1.0 this month as its distance grows from 171 million to 217 million km. Viewed telescopically, its gibbous disk (90% illuminated) appears only 7 arcseconds wide at midmonth.

The Moon lies 19° to the left of Mars on the 1st, passes close to Pollux in Gemini on the next night, lies above Regulus on the 5th and above Spica in Virgo on the 9th. Later in March, after passing Venus, the crescent Moon swings by Taurus again to lie 4° below the Pleiades on the 25th and a similar distance above-left of Mars on the 28th. By then Mars is passing 1° north of the star cluster M35 which sits some 3,000 light years away and, as I mentioned last month, is visible through binoculars.

Diary for 2023 March

Times are GMT until 26th, BST thereafter

  • 2nd 11h Venus 0.5° N of Jupiter
  • 3rd 03h Moon 1.7° S of Pollux
  • 4th 05h Moon 4°N of Praesepe
  • 6th 01h Moon 5° N of Regulus
  • 7th 13h Full Moon
  • 10th 11h Moon 3° N of Spica
  • 10th 20h Mars 5° S of Pollux
  • 14th 01h Moon 1.6° N of Antares
  • 15th 02h Last quarter
  • 16th 00h Neptune in conjunction with Sun
  • 17th 11h Mercury in superior conjunction on far side of Sun
  • 20th 21:24 Vernal equinox
  • 21st 17h New Moon
  • 22nd 20h Moon 0.5° S of Jupiter
  • 24th 10h Moon 0.1° S of Venus
  • 26th 00h Moon 1.9° S of Pleiades
  • 26th 01h GMT = 02h BST Start of British Summer Time
  • 26th 23h Moon 9° N of Aldebaran
  • 28th 14h Moon 2.3° N of Mars
  • 28th 15h Mercury 1.5° N of Jupiter
  • 29th 04h First quarter
  • 30th 11h Moon 1.6° S of Pollux
  • 30th 17h Venus 4° S of Pollux
  • 31st 07h Venus 1.3° N of Uranus
  • 31st 13h Moon 4°N of Praesepe

This is an extended version, with added diary, of Alan’s article published in The Scotsman on 28 February 2023, with thanks to the newspaper for permission to republish here.